A method for preparing stable plant protein hydrolyzed amino acid chelated cobalt

Abstract

This invention discloses a stable method for preparing cobalt chelated from plant protein hydrolyzed amino acids, comprising: step (1), adding a certain amount of water to a reaction vessel, heating to 40°C and starting stirring, adding plant protein hydrolyzed amino acids, and stirring until completely dissolved; step (2), after the amino acids are completely dissolved, adding cobalt chloride hexahydrate, stirring for five minutes, then uniformly adding trisodium citrate solution and stirring evenly, followed by gradient heating, while simultaneously starting ultrasound-assisted synthesis; step (3), after the synthesis reaction is completed, filtering the solution, and using spray drying to obtain the plant protein hydrolyzed amino acid chelated cobalt product. The amino acid chelated cobalt prepared by this invention has excellent stability, the operation process is simple, and it is suitable for production.

Description

Technical Field

[0001] This invention relates to the field of organic trace element chelates, specifically to a method for preparing a stable plant protein hydrolysate amino acid chelate cobalt. Background Technology

[0002] Amino acid chelated cobalt is an important class of trace element organic chelates. Its core component, cobalt, is an essential trace element for animals and humans. As a key component of vitamin B12, it participates in core physiological processes such as nucleic acid synthesis, energy metabolism, and hematopoiesis. Compared with traditional inorganic cobalt salts, amino acid chelated cobalt has significant advantages such as high stability, high bioavailability, and good palatability, and is widely used in related fields.

[0003] Plant-derived hydrolyzed amino acids are widely available, naturally safe, and have a balanced amino acid composition. Using them as raw materials to prepare amino acid chelated cobalt not only reduces production costs but also improves product biocompatibility, making it a hot research topic in the industry. However, in existing technologies, chelated cobalt products prepared from plant-derived hydrolyzed amino acids are prone to problems such as moisture absorption, discoloration, and chelate bond dissociation during production and storage, leading to poor product appearance, reduced purity, and insufficient stability, severely limiting their industrial application and market promotion. Therefore, developing a stable, simple, and controllable method for preparing plant-derived hydrolyzed amino acid chelated cobalt has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical defects of poor stability in existing plant protein hydrolyzed amino acid chelated cobalt products, and to provide a stable method for preparing plant protein hydrolyzed amino acid chelated cobalt. The amino acid chelated cobalt prepared by this invention has excellent hygroscopic stability, color stability, and chelate structure stability, and the operation process is simple, the parameters are easy to control, and it is suitable for large-scale industrial production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A stable method for preparing cobalt chelated from plant protein hydrolysate amino acids includes the following steps:

[0007] Step (1): Add a certain amount of water to the reactor, heat it to 40°C and start stirring, add plant protein hydrolysate amino acids, and stir until completely dissolved;

[0008] Step (2) After the amino acids are completely dissolved, add cobalt chloride hexahydrate, stir for five minutes, then uniformly add trisodium citrate solution and stir until homogeneous. Then, increase the temperature gradually and turn on the ultrasound to assist in the synthesis reaction.

[0009] After the synthesis reaction in step (3) is completed, the solution is filtered and the filtrate is spray-dried to obtain the plant protein hydrolysate amino acid chelated cobalt product.

[0010] Furthermore, in step (1), the source of the hydrolyzed amino acids of the plant protein is selected from soybean protein, pea protein or corn protein, with a degree of hydrolysis of 35%-55% and a total amino acid content of ≥80%.

[0011] Furthermore, in step (1), the mass ratio of the plant protein hydrolysate amino acids to cobalt chloride hexahydrate is 23.5:1.

[0012] Furthermore, in step (2), the mass of trisodium citrate is 5%-10% of the mass of cobalt chloride hexahydrate.

[0013] Furthermore, in step (2), the concentration of the trisodium citrate aqueous solution is 10-20%.

[0014] Furthermore, in step (2), the dripping rate of trisodium citrate is 5-10 ml / min.

[0015] Furthermore, in step (2), the gradient heating method is to heat up to 50°C at a rate of 5°C / min, hold for 30 min, then heat up to 85°C, hold for 2.2 h, and finally cool down to 70°C and hold for 1 h.

[0016] Furthermore, in step (2), the frequency of ultrasound assistance is 25 kHz.

[0017] Furthermore, in step (3), the inlet air temperature of the spray dryer is 180-210℃ and the outlet air temperature is 85-95℃.

[0018] In this invention, "%" refers to the percentage content by mass.

[0019] Compared with the prior art, the advantages of this invention are as follows:

[0020] This invention uses hydrolyzed amino acids from plant protein as chelating raw materials. The inventors have creatively discovered the synergistic effect between hydrolyzed amino acids and trisodium citrate: hydrolyzed amino acids are rich in various amino acid components and possess multiple coordination functional groups such as amino and carboxyl groups. These amino acid components can form a synergistic coordination effect, providing a solid foundation for the construction of the coordination structure. Based on this, trisodium citrate, as a ternary ligand, synergistically interacts with the multiple amino acids in the hydrolyzed amino acids in the early stages of the reaction, forming a stable ternary coordination structure with cobalt ions. Compared with traditional binary coordination structures, this significantly reduces the hygroscopic active sites of the product, inhibiting water adsorption and chelate bond dissociation. Simultaneously, by precisely controlling the amount, solution concentration, and dripping rate of trisodium citrate, the generation of byproducts caused by local reaction imbalances is avoided. Combined with gradient heating and ultrasonic-assisted processes, the stability and integrity of the ternary coordination structure are further enhanced. Furthermore, multiple stability testing methods comprehensively verify the product's moisture resistance, color stability, and chelate structure integrity during storage, solving the problems of easy moisture absorption, discoloration, and decreased chelation rate in existing technologies. Detailed Implementation Plan

[0021] To better understand the content of this invention, further description is provided below with reference to specific embodiments. It should be understood that these embodiments are only for further illustration of the invention and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art may make some non-essential modifications or adjustments to the invention, which still fall within the protection scope of this invention.

[0022] Stability test

[0023] 1. Moisture absorption stability test

[0024] Reference standard: GB / T 6284-2014 "General Method for Determination of Moisture in Chemical Products". Procedure: Take 5g of sample and spread it evenly on a 5cm diameter petri dish (2mm thick). Place it in a constant temperature and humidity chamber at 25±2℃, relative humidity 60±5%, and ventilation rate 0.3m / s. Weigh the sample after 40 hours and calculate the moisture absorption rate (moisture absorption rate = (mass after moisture absorption - initial mass) / initial mass × 100%) to determine the moisture resistance.

[0025] 2. Color stability test

[0026] Procedure: First, measure the initial color parameters of the sample (L brightness, a red-green value, b yellow-blue value). After storing the sample under the constant temperature and humidity conditions described above, remeasure the parameters periodically and calculate the color change value ΔE (ΔE=√[(ΔL)²+(Δa*)²+(Δb*)²]). The smaller the ΔE, the more stable the color. At the same time, record the time of visible color change.

[0027] 3. Chelation rate and retention rate test

[0028] Procedure: Accurately weigh the sample, dissolve it in 0.1 mol / L NaCl eluent, and filter to obtain the sample mother liquor; plot the cobalt standard curve; separate chelated cobalt and free cobalt using a gel column chromatography method, collect the two components separately, and make up to volume; quantify the cobalt content in the two components using atomic absorption spectrometry, calculating it according to the formula "chelation rate (%) = [mass of chelated cobalt / (mass of chelated cobalt + mass of free cobalt)] × 100%", taking the average of three parallel determinations, with RSD ≤ 2%. A higher chelation rate indicates a more complete chelated structure. Determine the initial chelation rate of the sample, and after storage under specified conditions, determine the chelation rate again, calculating the retention rate (retention rate = chelation rate after storage / initial chelation rate × 100%). A retention rate ≥ 90% indicates a stable chelated structure and no dissociation.

[0029] 4. Long-term stability testing

[0030] Procedure: Refer to GB / T 19458-2024 "Guideline for Long-Term Stability Testing of Chemicals". Take 3 parallel samples (5g each) and put them into aluminum-plastic composite sealed bags (with 1g of silica gel desiccant inside to simulate actual packaging). Place them in a constant temperature and humidity chamber at 25±2℃ and 60±5% relative humidity, away from light (no ventilation required, matching a sealed environment). Take samples for testing at 0 days (initial), 30 days, 60 days, 90 days, and 180 days (seal quickly after sampling to avoid secondary moisture absorption).

[0031] Preparation method of hydrolyzed amino acids from soybean protein: Soybean protein isolate was prepared into a 12.5% ​​aqueous solution and stirred until completely dissolved. The solution was heated to 55℃ and the pH was adjusted to 8.5 with 1 mol / L NaOH. Alkaline protease was added at an enzyme-to-protein ratio (E / S) of 3%, and the temperature was maintained at 55℃ and pH 8.5 for 2 hours of hydrolysis. Then, the temperature was raised to 95℃ and held for 15 minutes to inactivate the enzyme. After cooling, the enzyme-inactivated solution was filtered and spray-dried (inlet air 190℃, outlet air 85℃) to obtain hydrolyzed amino acid powder from soybean protein. The degree of hydrolysis was determined to be 45%, and the total amino acid content was 82%. The hydrolyzed amino acids from soybean protein used in the examples and comparative examples of this application were prepared using this method.

[0032] Example 1: Cobalt chelation with hydrolyzed amino acids from soybean protein (trisodium citrate synergist)

[0033] (1) Add 1500 ml of deionized water to the reactor, heat to 40 ℃ and start stirring, add 559.3 g of hydrolyzed amino acids of soybean protein (hydrolysis degree 45%, total amino acid content 82%), and stir until completely dissolved; add 23.8 g of cobalt chloride hexahydrate and stir evenly for 5 min;

[0034] (2) Dissolve 2g of trisodium citrate in 20ml of deionized water to prepare a 10% trisodium citrate solution; add the prepared trisodium citrate solution dropwise into the reaction vessel at a rate of 5ml / min and stir evenly for 5min; raise the temperature to 50℃ at a rate of 5℃ / min, keep it at that temperature for 30min, then raise the temperature to 85℃ and keep it at that temperature for 2.2h, and finally lower the temperature to 70℃ and keep it at that temperature for 1h, while turning on 25kHz ultrasound assistance;

[0035] (3) After the reaction is completed, the purple-red solution is filtered, and the filtrate is spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 90°C.

[0036] The actual yield of the product was 89.2%, the chelation rate was 96.1%, the color was purple, the content of chelated cobalt was 1.18%, and the moisture content was 1.12%.

[0037] HPLC analysis revealed 16 amino acids, including glutamic acid, aspartic acid, glycine, leucine, and lysine, with a total amino acid content of 86.3%. Among these, bound amino acids accounted for ≥98.2%, while free amino acids accounted for ≤1.8%.

[0038] Stability verification: Short-term stability verification (40h): moisture absorption rate 2.5%, color change ΔE=2.1, chelation retention rate 92.3%, no obvious color change; Long-term stability test (180 days, sealed): moisture absorption rate 3.8%, color change ΔE=3.5, no obvious color change, no clumping, free cobalt ion content 0.9%, chelation retention rate 86.5%.

[0039] Comparative Example 1: Cobalt-chelated amino acids from hydrolyzed soybean protein (without trisodium citrate)

[0040] (1) Add 1500ml of deionized water to the reactor, heat to 40℃ and start stirring, add 559.3g of hydrolyzed amino acids of soybean protein (hydrolysis degree 45%, total amino acid content 82%), and stir until completely dissolved; add 23.8g of cobalt chloride hexahydrate and stir evenly for 5min;

[0041] (2) Increase the temperature to 50℃ at a rate of 5℃ / min, hold for 30 min, then increase the temperature to 85℃, hold for 2.2 h, and finally decrease the temperature to 70℃ and hold for 1 h. Simultaneously turn on 25kHz ultrasound assistance;

[0042] (3) After the reaction is completed, the purple-red solution is filtered, and the filtrate is spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 90°C.

[0043] The actual yield of the product was 82.7%, the chelation rate was 95.8%, the color was light purple, the content of chelated cobalt was 1.17%, and the moisture content was 1.15%.

[0044] HPLC analysis revealed the presence of the same 16 amino acids as in Example 1, with a total amino acid content of 85.7%. However, the proportion of bound amino acids decreased to 95.3%, while the content of free amino acids increased to 4.7%. This indicates that in the absence of trisodium citrate, the coordination effect between the polyamino acids and cobalt ions is weakened, and the stability of the chelate structure decreases.

[0045] Stability verification: Short-term stability verification (40h): moisture absorption rate 4.3%, color change ΔE=3.9, water absorption and color change began after 8h, completely turned light pink after 16h, chelation retention rate 78.2%; Long-term stability test (180 days, sealed): moisture absorption rate 6.8%, color change ΔE=5.7, color turned light pink, obvious clumping, free cobalt ion content 3.5%, chelation retention rate 63.2%. Compared with Example 1, although the basic product performance is similar, the stability indicators are significantly different, proving the key synergistic effect of trisodium citrate on product stability.

[0046] Comparative Example 2: Cobalt chelation of hydrolyzed amino acids from soybean protein (excess trisodium citrate group)

[0047] (1) Add 1500ml of deionized water to the reactor, heat to 40℃ and start stirring, add 559.3g of hydrolyzed amino acids of soybean protein (hydrolysis degree 42%, total amino acid content 80%), and stir until completely dissolved; add 23.8g of cobalt chloride hexahydrate and stir evenly for 5min;

[0048] (2) Dissolve 3g of trisodium citrate in 20ml of deionized water to prepare a 15% trisodium citrate solution (the mass of trisodium citrate is 12.6% of cobalt chloride hexahydrate, exceeding the core ratio of 5%-10%); add the prepared trisodium citrate solution dropwise into the reactor at a rate of 5ml / min and stir evenly for 5min; raise the temperature to 50℃ at a rate of 5℃ / min, keep it at 30min, raise the temperature to 85℃, keep it at 2.2h, and finally lower the temperature to 70℃ and keep it at 1h, while turning on 25kHz ultrasound assistance;

[0049] (3) After the reaction is completed, the purple-red solution is filtered, and the filtrate is spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 90°C.

[0050] The actual yield of the product was 88.5%, the chelation rate was 91.2%, the color was purple, the content of chelated cobalt was 1.15%, and the moisture content was 1.14%.

[0051] HPLC analysis showed that the amino acid composition was basically the same as in Example 1, with a total amino acid content of 85.1%, a bound amino acid content of 96.1%, and a free amino acid content of 3.9%. This indicates that excessive trisodium citrate can prevent some amino acids from effectively participating in coordination, thereby reducing the overall structural stability.

[0052] Stability verification: Short-term stability verification (40h): moisture absorption rate 3.7%, color change ΔE=3.2, begins to absorb water and change color after 12h, completely turns light pink after 22h, chelation retention rate 82.5%; Long-term stability test (180 days, sealed): moisture absorption rate 5.3%, color change ΔE=4.8, color turns pinkish-purple, slight clumping, free cobalt ion content 2.8%, chelation retention rate 76.5%. This indicates that when the amount of trisodium citrate exceeds the limits defined in this invention, even if the performance of the basic product is close to that of Example 1, the stability cannot achieve the optimal effect, confirming the rationality and key role of the trisodium citrate dosage parameters in this invention.

[0053] Comparative Example 3: Cobalt-chelated amino acids from hydrolyzed soybean protein (disodium EDTA as a substitute)

[0054] (1) Add 1500ml of deionized water to the reactor, heat to 40℃ and start stirring, add 559.3g of hydrolyzed amino acids of soybean protein (hydrolysis degree 45%, total amino acid content 82%), and stir until completely dissolved; add 23.8g of cobalt chloride hexahydrate and stir evenly for 5min;

[0055] (2) Dissolve 2g of disodium ethylenediaminetetraacetate in 20ml of deionized water to prepare a 10% disodium ethylenediaminetetraacetate solution; add the prepared solution dropwise into the reaction vessel at a rate of 5ml / min and stir evenly for 5min; raise the temperature to 50℃ at a rate of 5℃ / min, keep it at that temperature for 30min, then raise the temperature to 85℃ and keep it at that temperature for 2.2h, and finally lower the temperature to 70℃ and keep it at that temperature for 1h, while turning on 25kHz ultrasound assistance;

[0056] (3) After the reaction is complete, the light purple-red solution is filtered, and the filtrate is spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 90°C.

[0057] The actual yield of the product was 87.3%, the chelation rate was 94.5%, the color was purple, the content of chelated cobalt was 1.16%, and the moisture content was 1.13%.

[0058] HPLC analysis showed that the amino acid composition was basically the same as in Example 1, with a total amino acid content of 85.9%. However, the proportion of bound amino acids was 94.7%, and the content of free amino acids was 5.3%. This indicates that although disodium ethylenediaminetetraacetate can chelate cobalt ions, its synergistic coordination ability with plant protein hydrolysate amino acids is weak, and it cannot form a stable ternary coordination structure.

[0059] Stability verification: Short-term stability verification (40h): Moisture absorption rate 3.2%, color change ΔE=2.8, slight water absorption and color change starting at 15h, basically turning pink after 40h, chelation retention rate 85.1%; Long-term stability test (180 days, sealed): Moisture absorption rate 4.9%, color change ΔE=4.2, color turning pinkish-purple with slight clumping, free cobalt ion content 2.1%, chelation retention rate 78.3%. Disodium EDTA is a traditional chelating agent. Although it can form a chelate structure with cobalt ions, its synergistic coordination ability with hydrolyzed amino acids from plant proteins is weaker than that of sodium citrate, and it cannot construct a stable ternary coordination structure. As a result, the chelation retention rate, moisture absorption stability, and other indicators are inferior to those in Example 1 after long-term storage. This comparative example further demonstrates that sodium citrate, as the synergistic chelating agent selected in this invention, is irreplaceable in improving product stability.

[0060] Comparative Example 4: Cobalt Chelated by Single Glycine

[0061] (1) Add 1500ml of deionized water to the reactor and heat it to 40℃ and start stirring. Add 566.3g of glycine and stir until dissolved. Add 23.8g of cobalt chloride hexahydrate and stir evenly for 5min.

[0062] (2) Increase the temperature to 50℃ at a rate of 5℃ / min, hold for 30 min, then increase the temperature to 85℃, hold for 2.2 h, and finally decrease the temperature to 70℃ and hold for 1 h. Simultaneously turn on 25kHz ultrasound assistance;

[0063] (3) After the reaction is completed, the purple-red solution is filtered, and the filtrate is spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 90°C.

[0064] The actual yield of the product was 91.2%, the chelation rate was 81.3%, the color was purple, the content of chelated cobalt was 1.16%, and the moisture content was 1.13%.

[0065] HPLC analysis revealed that only glycine was detected, with a total amino acid content of 92.1%, bound amino acids accounting for 89.5%, and free amino acids accounting for 10.5%. This indicates that the single amino acid system cannot form a multi-component synergistic coordination structure, resulting in a significant decrease in stability.

[0066] Stability testing: Short-term stability verification (40h): moisture absorption rate 4.8%, color change ΔE=4.7, began to absorb water and change color after 6h, completely turned pink after 10h, chelation retention rate 75.6%; Long-term stability testing (180 days, sealed): moisture absorption rate 7.5%, color change ΔE=6.2, color turned light pink, obvious clumping phenomenon, free cobalt ion content 4.2%, chelation retention rate 59.8%. This indicates that the addition of trisodium citrate alone, without the multi-component synergy of hydrolyzed plant protein amino acids, makes it difficult to form a stable ternary structure. Even though the performance of the basic product is similar to that of Example 1, the stability still declines significantly, further highlighting the synergistic effect mechanism of trisodium citrate and hydrolyzed plant protein amino acids in this invention.

[0067] Comparative Example 5: Single glycine chelated cobalt (trisodium citrate synergist group)

[0068] (1) Add 1500ml of deionized water to the reactor, heat to 40℃ and start stirring, add 566.3g of glycine (the same amount as in Comparative Example 2), and stir until completely dissolved; add 23.8g of cobalt chloride hexahydrate and stir evenly for 5min;

[0069] (2) Dissolve 2 g of trisodium citrate in 20 ml of deionized water to prepare a 10% trisodium citrate solution (the amount is the same as in Example 1); add the prepared trisodium citrate solution dropwise into the reaction vessel at a rate of 5 ml / min and stir evenly for 5 min; raise the temperature to 50 ℃ at a rate of 5 ℃ / min, keep it at that temperature for 30 min, then raise the temperature to 85 ℃ and keep it at that temperature for 2.2 h, and finally lower the temperature to 70 ℃ and keep it at that temperature for 1 h, while turning on 25 kHz ultrasound assistance;

[0070] (3) After the reaction is completed, the purple-red solution is filtered, and the filtrate is spray-dried with an inlet air temperature of 180 ℃ and an outlet air temperature of 90 ℃.

[0071] The actual yield of the product was 90.5%, the chelation rate was 89.7%, the color was light purple, the content of chelated cobalt was 1.17%, and the moisture content was 1.14%.

[0072] HPLC analysis revealed that only glycine was detected, with a total amino acid content of 91.7%, bound amino acids accounting for 92.1%, and free amino acids accounting for 7.9%. This indicates that even with the addition of trisodium citrate, glycine alone cannot form a multi-component synergistic coordination structure, and its stability is far lower than that of Example 1.

[0073] Stability Tests: Short-term stability verification (40h): Moisture absorption rate 3.5%, color change ΔE=3.1, slight water absorption and color change starting at 8h, turning light pink at 18h, chelation retention rate 81.2%; Long-term stability test (180 days, sealed): Moisture absorption rate 6.1%, color change ΔE=5.3, color turning light pink with slight clumping, free cobalt ion content 3.8%, chelation retention rate 68.4%. The only difference between this comparative example and Example 1 is that "hydrolyzed amino acids from plant protein" is replaced with "single glycine". Although the same amount of sodium citrate was added, the stability index was still significantly worse than that of Example 1. The core reason is that single glycine has a single functional group, and the coordination structure formed with sodium citrate and cobalt ions has poor stability, and it cannot build a stable ternary coordination system like hydrolyzed amino acids from plant protein (multiple amino acid synergy). This further proves that the core advantage of this invention is the synergistic effect of "hydrolyzed amino acids from plant protein + sodium citrate", rather than the effect of sodium citrate alone.

[0074] Application Simulation of Water-Soluble Fertilizer Application Examples

[0075] To verify the applicability of the amino acid chelated cobalt of the present invention in the field of fertilizer, the soybean protein hydrolyzed amino acid chelated cobalt (trisodium citrate synergist group) prepared in Example 1 was used as an organic cobalt source and applied to a water-soluble fertilizer system containing macro-elements.

[0076] Following the conventional formula for amino acid-containing water-soluble fertilizers, the product of this invention was added to a water-soluble fertilizer at a ratio of 8 g / kg, mixed with urea, potassium dihydrogen phosphate, potassium chloride, and conventional trace elements (calcium, magnesium, iron, and zinc chelates). Deionized water was added and stirred to dissolve the mixture. The pH was adjusted to 6.0-6.5, and after filtration, a clear and transparent liquid water-soluble fertilizer was obtained. This water-soluble fertilizer was stored in sealed containers and subjected to storage at 25°C and 60% relative humidity for 90 days, and at 35°C and 75% relative humidity for 60 days, simulating different regional storage and transportation conditions. After storage, the water-soluble fertilizer was diluted 1000 times to simulate drip irrigation application conditions.

[0077] The results show:

[0078] Under both storage conditions, the water-soluble fertilizer remained clear and transparent, without any sedimentation, layering, or turbidity, and the color change was slight (ΔE≤3.4), indicating that the product of this invention has good stability in the water-soluble fertilizer system.

[0079] After storage, the chelation retention rate of the product of this invention remained above 78%, which was significantly higher than that of the control group without sodium citrate and the commercially available inorganic cobalt source, indicating that it could still maintain structural stability in a water-soluble fertilizer system with high salt and high ionic strength.

[0080] The product of this invention does not exhibit significant antagonistic reactions with nitrogen, phosphorus, potassium, and other trace elements, and does not show common problems such as phosphorus precipitation, demonstrating good compatibility.

[0081] The diluted water-soluble fertilizer showed no clogging during the simulated drip irrigation process, and the cobalt element was evenly distributed, making it suitable for modern agricultural fertilization methods such as drip irrigation and sprinkler irrigation.

[0082] In summary, the product of this invention, as an organic cobalt source in water-soluble fertilizers, has excellent storage stability, compatibility, and application adaptability. It can effectively improve the stability and availability of cobalt in fertilizer systems and is suitable for large-scale agricultural applications.

[0083] The systematic verification of the above examples and comparative examples fully demonstrates that trisodium citrate, as a dedicated stability enhancer, can synergistically construct a stable ternary coordination structure with hydrolyzed amino acids from plant proteins. This is the core key to improving the stability of amino acid chelated cobalt. This invention, by precisely controlling the dosage, solution concentration, and dropping rate of trisodium citrate, fully leverages its multi-faceted synergistic advantages with hydrolyzed amino acids from plant proteins, ultimately achieving a breakthrough improvement in product stability. This technical solution is simple and controllable, adaptable to the needs of industrial production, and successfully overcomes the core technical pain points of existing technologies, such as the hygroscopic nature, discoloration, and chelation rate decay after long-term storage of amino acid chelated cobalt.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions also fall within the protection scope defined by the appended claims.

Claims

1. A method for preparing stable plant protein hydrolysate amino acid chelates of cobalt, comprising: Step (1): Add a certain amount of water to the reactor, heat it to 40°C and start stirring, add plant protein hydrolysate amino acids, and stir until completely dissolved; Step (2): After the amino acids are completely dissolved, add cobalt chloride hexahydrate, stir for five minutes, then uniformly add trisodium citrate solution and stir until homogeneous. Then, increase the temperature gradually and turn on the ultrasound to assist the synthesis reaction. Step (3): After the synthesis reaction is completed, the solution is filtered and the filtrate is spray-dried to obtain plant protein hydrolysate amino acid chelated cobalt product.

2. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (1), the source of the hydrolyzed amino acids of the plant protein is selected from soybean protein, pea protein or corn protein, with a degree of hydrolysis of 35%-55% and a total amino acid content of ≥80%.

3. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (1), the mass ratio of the plant protein hydrolysate amino acids to cobalt chloride hexahydrate is 23.5:

1.

4. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (2), the mass of trisodium citrate is 5%-10% of the mass of cobalt chloride hexahydrate.

5. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (2), the concentration of the trisodium citrate aqueous solution is 10-20%.

6. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (2), the dripping rate of trisodium citrate is 5-10 ml / min.

7. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (2), the gradient heating method is to heat up to 50°C at a rate of 5°C / min, hold for 30 min, then heat up to 85°C, hold for 2.2 h, and finally cool down to 70°C and hold for 1 h.

8. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (2), the frequency of ultrasound assistance is 25 kHz.

9. The method for preparing stable plant protein hydrolyzed amino acid chelated cobalt as described in claim 1, characterized in that, In step (3), the inlet air temperature of the spray dryer is 180-210℃ and the outlet air temperature is 85-95℃.

10. The method for preparing stable plant protein hydrolysate amino acid chelated cobalt as described in claim 1, characterized in that, In step (1), the hydrolyzed amino acids of plant protein are prepared by the following method: Soy protein isolate is prepared into a 12.5% ​​aqueous solution, stirred until completely dissolved, heated to 55℃ and pH adjusted to 8.5 with 1 mol / L NaOH, alkaline protease is added at an enzyme-to-protein ratio (E / S) of 3%, and the temperature is maintained at 55℃ and pH 8.5 for 2 h of hydrolysis; then the temperature is raised to 95℃ and kept at 15 min to inactivate the enzyme, the enzyme-inactivated solution is cooled and filtered, and spray-dried to obtain the hydrolyzed amino acids of plant protein.